North Korean leader Kim Jong Un watches the ballistic rocket launch drill of the Strategic Force of the Korean People's Army (KPA) at an unknown location, in this undated file photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang in March 2016. Photo: Reuters/File Photo

North Korea fired three ballistic missiles early on Tuesday which flew between 500 and 600 kms (300 and 360 miles) into the sea off its east coast, South Korea's military said, the latest in a series of provocative moves by the isolated country.

The missiles, which South Korea's Yonhap News Agency said were presumed to be Scud types, were launched from an area in the North's western region called Hwangju between 5:45 a.m. local time (2045 GMT Monday) and 6:40 a.m., the South's military said.

Tuesday's launches came days after South Korea and the United States announced a final decision to deploy the Terminal High Altitude Area Defence (THAAD) anti-missile system in the South to counter threats from the North.

"The ballistic missiles flight went from 500 km to 600 km, which is a distance far enough to strike all of South Korea including Busan," the South's military said in a statement.

Busan is a South Korean port city in the south.

North Korea has test-fired a series of ballistic missiles in recent months, in defiance of United Nations Security Council resolutions, including intermediate-range missiles in June and a submarine-launched missile this month.

North Korea's military had threatened to retaliate against the deployment of the THAAD system with a "physical response" once its location and time of installation were decided.

China has also sharply criticized the decision to base a THAAD battery in South Korea, saying the move will destabilize the security balance in the region.

North Korea conducted its fourth test of a nuclear device in January, and activity at its nuclear test site has increased recently, according to media reports in South Korea and Japan citing government officials, as well as a report by Washington-based North Korea monitoring project 38 North.

Following Pyongyang's January nuclear test and a February space rocket launch that was widely viewed as a missile test in disguise, the U.N. Security Council imposed tough new resolutions that further isolate North Korea.

In addition to the decision to base a THAAD system in South Korea, the United States recently angered North Korea by blacklisting its leader Kim Jong Un for human rights abuses.